The present invention relates generally to systems and methods for indicating acoustic energy power output, and more particularly to systems and methods for measuring power of acoustic energy transmitted by an ultrasound transducer, such as a focused ultrasound transducer.
Focused ultrasound systems have been suggested for directing acoustic energy towards a target tissue region within a patient, such as a cancerous or benign tumor, to necrose or otherwise treat the tissue region with thermal energy. For example, a piezoelectric transducer located outside the patient""s body may be used to focus high intensity acoustic waves, such as ultrasonic waves (acoustic waves with a frequency greater than about twenty kilohertz (20 kHz), and more typically between fifty KiloHertz and five MegaHertz (0.05-5 MHz)), at an internal tissue region of a patient to therapeutically treat the tissue region. The ultrasonic waves may be used to ablate a tumor, thereby obviating the need for invasive surgery. Such a sonic transducer system is disclosed in U.S. Pat. No. 4,865,042 issued to Umemura et al.
The acoustic energy emitted from such a system may be focused at a desired focal zone to provide a desired energy level in the target tissue region. To increase the size of the necrosed region, more acoustic energy may be applied to the focal zone, for example, by increasing the amplitude of the ultrasonic waves. This generally increases the size of the tissue region that is necrosed at the focal zone by the sonication, and consequently may reduce the number of sonications needed to treat an entire tissue structure, such as a tumor. Increasing the ultrasonic power, however, also increases the amount of energy that passes through the tissue on either side of the focal zone. This may cause undesired pain to the patient, heating, and/or necrosis of tissue outside of the target region, particularly in the xe2x80x9cnear field,xe2x80x9d i.e., the region between the transducer and the focal zone. Thus, it is important to precisely control the amount of acoustic energy delivered to a patient.
Controlling the amount of acoustic energy delivered to a patient requires knowledge of the ultrasonic power output of the transducer system. Though power output may be calculated theoretically, actual measurements are necessary to account for changes that may occur in the system over time and/or for variations in manufacturing, materials and environment.
Accordingly, apparatus, systems and, methods for indicating ultrasonic power output from a focused ultrasound transducer would be considered useful.
The present invention is directed to apparatus, systems, and methods for indicating or measuring power output from an ultrasound transducer, such as a focused ultrasound transducer.
For example, an ultrasound transducer may include one or more piezoelectric transducers, drive circuitry coupled to the transducer, and a controller coupled to the drive circuitry. The drive circuitry may be configured for providing drive signals to the transducer such that the transducer emits acoustic energy towards a target tissue region within a patient""s body. The controller may be configured for controlling the drive circuitry to change parameters of the drive signals, e.g., frequency, amplitude, and/or phase, and/or to perform other operations.
An apparatus or system for indicating or measuring the power of the acoustic energy transmitted by an ultrasound transducer may include a container or housing including one or more fluids therein, such as degassed water, and a buoyant body floating at a first level in the fluid. By impacting the buoyant body with acoustic energy, e.g., converging ultrasonic waves, output by the ultrasound transducer, the buoyant body may float at a second, different level in the fluid. Under certain conditions, the displacement of the buoyant body from the first level to the second level may correspond to the power of the acoustic energy transmitted by the ultrasound transducer. The buoyant body may have a wave receiving surface positioned at least partially in or adjacent to the region towards which the acoustic energy is directed. The wave receiving surface may be oriented towards the transducer such that acoustic energy transmitted from the transducer may strike the wave receiving surface, thereby causing the buoyant body to float at a different level within the fluid.
The apparatus or system may output one or more signals, such as electrical signals and/or wireless signals, corresponding to the level at which the buoyant body floats and/or corresponding to displacement of the buoyant body relative to a reference point. The signals may be routed to a controller coupled to the ultrasound transducer for controlling the power output of the ultrasound transducer.
A method is also provided for measuring power of acoustic energy transmitted by an ultrasound transducer. A buoyant body may be provided floating at a first level in a fluid adjacent an ultrasound transducer. For example, a container including one or more fluids therein may be disposed adjacent the transducer, and the buoyant member may be provided floating or suspended in the fluid at the first level when the transducer is inactive.
Acoustic energy, e.g., ultrasonic waves, may be directed from the ultrasound transducer towards a surface of the buoyant member, causing the buoyant member to float at a second level in the fluid. Displacement of the buoyant member from the first level to the second level may be used to indicate the power of the acoustic energy directed against the surface. Optionally, one or more signals, e.g., electrical and/or wireless signals, related to the level of the buoyant body may be generated, and the signals may be used to control the power output from the ultrasound transducer.
Other objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.